1. Field of the Invention
The present invention relates to a liquid ejection head, an image forming apparatus and a method of manufacturing a liquid ejection head, and more particularly, a liquid ejection head having a structure in which a plurality of plate members are arranged to overlap each other.
2. Description of the Related Art
There is known, as an image forming apparatus, an inkjet recording apparatus which comprises a print head (liquid ejection head) having an arrangement of a plurality of nozzles (ejection ports) and which forms images on a recording medium by ejecting ink droplets from the nozzles toward the recording medium while causing the print head and the recording medium to move relatively to each other.
A print head of an inkjet recording apparatus of this kind comprises, for example, a common liquid chamber which accumulates ink to be supplied to the ink tank, pressure chambers to which ink is supplied from the common liquid chamber through ink supply ports, a diaphragm constituting one wall of the pressure chambers, piezoelectric elements provided on the diaphragm at positions corresponding to the pressure chambers, and nozzles connected to the pressure chambers. When a piezoelectric element is driven by applying an electric signal corresponding to the image data, in a state where the pressure chamber is filled with ink, then the volume of the pressure chamber is decreased by the deformation of the diaphragm, and the ink inside the pressure chamber is ejected from the nozzles in the form of an ink droplet, thereby forming a dot on the recording medium. By combining dots of this kind, an image is formed on the recording medium.
In recent years, it has become desirable to form images of high quality on a par with photographic prints, in inkjet recording apparatuses of this kind. To achieve this, it is necessary to reduce the size of the ink droplets ejected from the nozzles by reducing the nozzle size, as well as increasing the number of pixels per unit surface area by arranging the nozzles at high density. Furthermore, together with the increase in image quality, there have also been demands for improved printing speed, and therefore, it is important to improve ink supply performance (refilling performance) from the common liquid chamber to the pressure chambers, in such a manner that high-frequency driving of the nozzles and ejection of high-viscosity ink can be achieved.
In order to improve productivity and reliability in a print head, various proposals have been made for manufacturing a print head using ceramic (see Japanese Patent Application Publication Nos. 6-234218, 2001-353866 and 2000-108342.) In Japanese Patent Application Publication No. 6-234218, a pressure generation units for generating pressure for projecting ink droplets is constituted by integrated sintering of ceramic, in such a manner that liquid sealing characteristics can be ensured in a reliable manner. However, a composition is adopted in which the individual electrodes of piezoelectric elements (drive signal application electrodes) are extracted to external wires at the end sections of the diaphragm, in such a manner that they pass over the surface of the diaphragm which is made of ceramic, and hence there are limitations on the installation of high-density wiring and this composition is not suitable for achieving high nozzle density.
In Japanese Patent Application Publication No. 2001-353866, flow channels, such as a common liquid chamber and pressure chambers (pressurization liquid chambers) are fabricated by performing sandblasting or dry-etching in glass or ceramic, and therefore it is possible to fabricate a print head by using inexpensive materials, by means of a relatively simple process. However, extraction electrodes are provided in the same plane as individual electrodes provided opposing the diaphragm at a uniform interval from same, and therefore, similarly to Japanese Patent Application Publication No. 6-234218, there are limitations on the installation of high-density wiring. Moreover, the manufacturing process is complicated and expensive.
In Japanese Patent Application Publication No. 2000-108342, pressure generating chamber units made of silicon and flow channel units made of ceramic are bonded together without using adhesive, in such a manner that the manufacturing process of a print head is simplified and reliability can be improved. However, there is absolutely no description of the composition of the wiring for connecting the individual electrodes and the common electrode of the piezoelectric elements provided on the diaphragm at positions corresponding to the pressure chambers, with the drive circuits. For example, if the wires are provided so as to pass over the surface of the diaphragm, as in Japanese Patent Application Publication No. 6-234218, then the wiring space is insufficient and there are restrictions on the installation of high-density wiring. Furthermore, if the common liquid chamber is made large in size, then deterioration of accuracy becomes a concern.